Safety evaluations at each visit will include a history, and physical exam and mental status exam, blood and urine tests, and lung function tests. The main physiologic outcome of the trial will be the assessment of salt and water transport NPD. In this way, we will assess whether genistein enhances the effect of phenylbutyrate to improve chloride transport in the nose by topical application of genistein to the nasal mucosa during the NPD procedure on study days 1 and 7.